1. Technical Field
The present invention relates to a thin film type common mode filter, and more particularly, to a thin film type common mode filter including an internal electrode manufactured in a coil electrode form and provided with a simultaneous coil pattern in which two coil electrodes are overlapped with each other in a single layer in a direction in which a coil is wound, wherein a height of a second insulating layer formed on the internal electrode is higher than an interval between the coils to decrease a parasitic capacitance component.
2. Description of the Related Art
Recently, electronic devices such as cellular phones, electric home appliances, personal computers (PCs), personal digital assistants (PDAs), liquid crystal displays (LCDs), navigations, or the like, have been digitized and accelerated. Since the electronic devices are susceptible to a stimulus from the outside, a circuit is damaged or a signal is distorted in the case in which a small level of abnormal voltage and a high frequency noise are introduced from the outside into an internal circuit of the electronic device.
The abnormal voltage and the noise are resulted from a switching voltage generated in the circuit, a power supply noise included in a power supply voltage, unnecessary electromagnetic signal, and an electromagnetic noise, or the like, and a common mode filter (CMF) has been used as a means for preventing the abnormal voltage and the noise from being introduced to the circuit.
In general, in a differential signal transmission system, a passive component such as a diode, a varistor, or the like, has been separately used in order to suppress an electro static discharge (ESD) generated at input and output terminals together with the CMF for removing a common mode noise.
FIGS. 1A and 1B are schematic diagrams showing a structure of a common mode filter of the related art. Referring to FIGS. 1A and 1B, the general common mode filter includes a base substrate 1, a first insulating layer 2 formed on the base substrate 1, an internal electrode 3 formed on the first insulating layer 2, a second insulating layer 4 formed on the first insulating layer 2 so as to receive the internal electrode 3, an external electrode terminal 5 formed on the second insulating layer 4 so as to ground an exposed end of the internal electrode 3, and a ferrite resin layer 6 formed on the second insulating layer 4.
However, in the above-mentioned common mode filter of the related art, a parasitic capacitance is generated due to structural properties.
A region indicated by the part “A” of FIGS. 1A and 1B is a region at which the parasitic capacitance is generated.
As shown in FIG. 1A, the parasitic capacitance is intensively generated at different electrified circuits, that is, above and below a vicinity at which the internal electrode 3 and the external electrode terminal 5 are mutually close to each other, in particular, in the vicinity of a boundary therebetween.
In addition, as shown in FIG. 1B, the parasitic capacitance is generated between a plurality of internal electrodes 3 formed in each layer.
The internal electrode 3 of the related art is manufactured in a coil form, and a structure thereof in the related art having different forms of coils formed in a single layer cannot but generate the parasitic capacitance. In addition, the parasitic capacitance is a main reason that a self resonant frequency (SRF) is damaged.